Lithium batteries, in particular lithium secondary batteries, having such characteristics as a large energy density and a long life, are used widely as power 3669344. DOC 1 sources for home appliances such as video cameras and portable electronic devices such as notebook personal computers and cellular phones; recently, applications into large batteries that equip an electric vehicle (EV), a hybrid electric vehicle (HEV) and the like, are anticipated.
A lithium secondary battery is a secondary battery having a structure in which, during charging, lithium dissolves out from the positive electrode as an ion and moves towards the negative electrode to be stored and conversely, during discharging, the lithium ion returns from the negative electrode to the positive electrode, and it is known that the high energy density of the battery has its source mainly in the electric potential of the positive electrode material.
In addition to lithium transition metal oxides such as LiCoO2, LiNiO2 and LiMnO2 having a layer structure, lithium manganese based composite oxides (LMO) such as LiMnO4 and LiNi0.5Mn0.5O4 are known as positive electrode active materials for lithium secondary batteries. Among these, owing to the low raw material costs, the absence of toxicity and safety, there is a focus on the lithium manganese based composite oxides (LMO) as a positive electrode active material for a large battery for an electric vehicle (EV), a hybrid electric vehicle (HEV) and the like. In addition, while excellent output characteristics are particularly demanded of a battery for an EV or HEV, on this point, compared to a lithium transition metal oxide such as LiCoO2, which has a layer structure, a spinel-type lithium manganese-based composite oxide (LMO), which allows for insertion and desorption of Li ions three-dimensionally, has excellent output characteristics.
Regarding this species of spinel-type lithium manganese-based composite oxide (LMO), as a positive electrode active substance that, at the same time as being of low internal resistance, high output and high capacity, demonstrates excellent charge-discharge cycle characteristics even under high-temperature conditions, a positive electrode active substance is described in Patent Document 1, containing the lithium transition metal composite oxide represented by the general formula LiXMYOZ-δ (where M represents a transition metal element Co or Ni, the relationships (X/Y)=0.98 to 1.02 and (δ/Z)≦0.03 are fulfilled) and at the same time containing with respect to the transition metal element (M) constituting the lithium transition metal composite oxide, ((V+B)/M)=0.001 to 0.05 (molar ratio) of vanadium (V) and/or boron (B), whereof the primary particle size is 1 μm or greater, the crystallite size is 450 Å or greater and the lattice strain is 0.05% or less.
Described in Patent Document 2 is a positive electrode active substance for lithium secondary battery in which the ratio between the median diameters D50 of the positive electrode active substance determined by laser diffraction when the positive electrode active substance was dispersed into ethanol and ultrasonic was applied and not applied (the value of D50 (no ultrasonic)/D50 (with ultrasonic)) is 1 to 2.
As a novel positive electrode active substance material for lithium battery that allows the filling density (tap density) to be raised and simultaneously allows the output characteristics to be raised, a positive electrode active substance material for lithium battery is described in Patent Document 3, containing a spinel-type (space group Fd-3m) lithium transition metal oxide and a boron compound, the spinel-type lithium transition metal oxide being represented by general formula Li1+XM2-XO4-δ (where M is a transition metal containing Mn, Al and Mg; x is 0.01 to 0.08; and 0≦δ), in which, as measured by the Rietveld method using the fundamental method, the inter-atomic distance Li—O is 1.971 Å to 2.006 Å and the crystallite size is 500 nm to 2,000 nm.
As a novel spinel-type lithium transition metal oxide (LMO) with excellent output characteristics that preferably may combine output characteristics and high-temperature cycle life span characteristics, an LMO is described in Patent Document 4, in which, as measured by the Rietveld method using the fundamental method, the inter-atomic distance Li—O is 1.971 Å to 2.006 Å and the crystallite size is 170 nm to 490 nm in a lithium transition metal oxide represented by general formula Li1+XM2-XO4 (where M is a transition metal containing Mn, Al and Mg; and x is 0.01 to 0.08).
In addition, as a positive electrode active substance that enables fabrication of a lithium secondary battery in which high-temperature cycle characteristics are improved while the rate characteristics are also excellent, with satisfactory coating ability, a positive electrode active substance is described in Patent Document 5, containing crystal particles comprising lithium manganate of a spinel structure that contains lithium and manganese as constitutive elements, in which the average primary particle size is 1 μm or greater but less than 5 μm, the crystallite size in the powder x-ray diffraction pattern is 500 to 1500 nm, the value of lattice strain (η) is 0.05×10-3 to 0.9×10-3, and the ratio D50/DBET between the median diameter D50 (μm) thereof and DBET (μm) calculated from the BET specific surface area using general formula (1) is 1 to 4.